1. Field of the Invention:
The present invention related to the field of pumps.
2. Description of the Prior Art:
Several different types of fuel combustion engines have been offered as alternatives to the familiar, reciprocating piston-type internal combustion engines, such as are universally used in automobiles, motorcycles, small airplanes, etc. One of the reasons these alternatives have been proposed is that piston-type engines are relatively inefficient, at least partly the result of having to convert linearly reciprocating piston motion into rotary crank shaft movement. Another reason is that the ratio of piston engine weight to output (brake) horsepower is relatively unfavorable for many applications.
Of these proposed alternatives, gas turbine engines have proven more successful, replacing piston engines in many applications, such as in aircraft, where high power and low weight to horsepower ratios are essential. Nevertheless, because of high cost and various problems, turbine engines have not, for example, proven competitive with piston engines for most other uses, including automotive use, due at least partly to general economy of, and satisfaction with, piston engines for these applications, with consequent lack of turbine engine development effort in these areas.
Also seriously proposed as an alternative to the piston engine, or in many instances a supplement to such engines, are rotary or orbital engines. Rotary engines can be divided into two sub-types--the Wankel rotary piston engine employing a triangular rotor which functions much like a piston in a reciprocating engine, and vane-type, orbital or concentric rotating engines which ordinarily employ a number of vanes radially sliding from a rotor to circumferentially divide a large central chamber into a number of smaller working chambers which are compressed and expanded as the rotor orbits the combustion chamber. When the rotor is driven, instead of being used to drive, for example, a drive shaft, and with relatively minor modifications as alternatives, the orbital or rotary "engine" can be utilized as an orbital or rotary pump. Thus, in most respects, discussion of an orbital and rotary combustion engines can be considered to apply, as well, to the corresponding orbital and rotary pumps, with advantages of such engines and pumps being generally similar. Exemplary of rotary engines are the patent disclosures of Hoffman, Hutsell, Vawter, Howitt et al., Chkliar, Rhine, Kelly and Bentley (U.S. Pat. Nos. 1,121,628; 1,269,937; 1,303,134; 1,354,189; 2,179,401; 2,302,254; 3,452,725 and 3,762,375, respectively).
In general, rotary engines differ from reciprocating piston engines in that the high pressure gases created by combustion of a fuel-air mixture in each of the working chambers in sequence drives the rotor in an orbital direction around the central chamber or concentric with the chamber, the rotor in turn causing rotation of the crank shaft to which it is connected. There is no linear reciprocating movement, as is present in piston-type engines, which must be converted to rotary shaft movement.
Thus, at least in concept, concentric rotary or orbital engines (and pumps) are comparatively simple, and Wankel engines have achieved some success, particularly as automobile engines for Mazda automobiles. However, because of relatively high fuel consumption, high exhaust emission of air pollutants and relatively low reliability and short life, in spite of initial good engine performance, use of Wankel engines has been limited and interest in this type engine has currently greatly diminished in the face of fuel shortages, high fuel costs and stringent exhaust emission standards.
A major problem, if not the major problem, with rotary engines (and pumps) has been sealing between the rotor or rotor vanes and inner housing walls which form the combustion (or pumping) chamber. In piston-type engines sealing is relatively easy and straightforward--each cylinder is constructed to be entirely separate and the cylindrical portions which slide linearly in cylindrical chambers are relatively easily sealed by one or more circular piston rings. However, in rotary engines (and pumps) each of the several working chambers are separated only by contact between edges of the rotor or rotor vanes and the engine housing inner walls. The high pressure differential across these contact regions, between adjacent working chambers makes sealing very difficult. When sliding vanes are used with the rotor, as they are in orbital-type or concentric rotating rotary engines (and pumps), large bending moments are applied to the vanes by high pressure combustion gases (or pumped fluids including gases). This tends not only to inhibit free sliding of the vanes radially in and out of the rotor as the rotor orbits about its chamber, as is necessary to maintain sliding engagement with the housing walls, but also to damage the vanes.
Furthermore, the inner housing walls are generally constructed with a non circular transverse cross section such that the rotor or vane contact regions change their angle of contact as the rotor revolves concentrically or orbits about the chamber. This adds to the side loading of vanes and greatly enhances the difficulty of sealing between the rotor or vanes and the housing walls. Resultant leakage of high pressure combustion gases (or fluids being pumped) from one working chamber to adjacent chambers causes loss of compression and exhaust emission of improperly combusted fuel (or low pumping pressures).
In addition to problems with sealing, there are substantial difficulties with valving combustion air into, and exhaust gases from, the working chambers of rotary-type engines (and similarly with valving of fluid inlet and outlet to the chamber for pumps). Such valving is less straightforward in rotary engines (and pumps) than in piston engines because of orbital or rotary movement of the rotor.
Although, at least in theory, rotary and orbital type engines (and pumps) appear to offer substantial advantages over piston type internal combustion engines (and conventional pumps), for reasons including those set forth above, such engines (and corresponding pumps) heretofore available have been costly to produce, have required frequent repairing and have been generally unsatisfactory. As a result, substantial improvements to rotary and orbital engines (and pumps) are required before their full potential can be realized.